1. Field of the Invention
The invention relates to a feed pump for feeding fuel out of a fuel tank of a motor vehicle or for feeding washing fluid of a windshield washing system including a casing, an impeller arranged in the casing and connected on a driven shaft such that the impeller is fixed with respect to rotation relative to the driven shaft and a portion of the impeller is arranged with a slight clearance relative to the casing.
2. Description of the Related Art
Feed pumps for feeding fuel out of a fuel tank or for feeding washing fluid for a windshield washing system are typically designed as peripheral pumps or side-channel pumps and are known from practice. Each of these known pumps includes a casing which usually has two casing parts with a recess for the impeller. A particularly small sealing gap is arranged between the impeller and the casing parts in radially outer regions of the impeller which are adjacent to guide blades. An axial sliding bearing is usually also arranged in the sealing gap.
A problem with the known feed pump is that positional tolerances and the angle of inclination of the shaft with respect to the casing may lead to the impeller rubbing on the casing. This rubbing generates loud noises and, moreover, reduces the efficiency of the feed pump.
The object of the present invention is to provide a feed pump such that it generates a particularly low level of noise and has as high an efficiency as possible.
The object of the present invention is met by a feed pump including an impeller arranged on a shaft and having means for the movability of a radially outer region of the impeller in a pivoting direction relative to the shaft about an axis arranged transversely to the shaft and/or in an axial direction relative to a radially inner region of the impeller.
This configuration allows the radially outer region of the impeller to be tilted or slightly displaced by an intended amount in the casing. The position may be adjusted in the casing, for example, by the forces of the axial bearing of the impeller. Rubbing of the impeller on the casing is reliably avoided as a result. Furthermore, the formation of noise is kept particularly low due to the present invention. The feed pump according to the present invention has particularly high efficiency due to the constant sealing gap in the region adjacent to the guide blades.
To generate the pivotability of the impeller with respect to the shaft, a particularly large play may be arranged between the impeller and the shaft. However, the large play produces rattling noises when the shaft is driven and in the case of fluctuations in flow in the feed pump. According to an embodiment of the present invention, rattling noises may be kept particularly low when the impeller has, in its region adjacent to the shaft, a depression which surrounds the shaft. This configuration allows the connection of the impeller to the shaft to be restricted to intended dimensions for an intended height of the impeller. In the case of the very small play of the impeller with respect to the shaft, these dimensions are critical for the intended pivotability of the impeller. Another advantage of this configuration is that the impeller does not rub on the casing in the region of the depression.
The depression may be arranged on one end face of the impeller. However, the generation of noise in the feed pump according to the present invention is further reduced when a depression is arranged in each of the two end faces of the impeller.
According to another embodiment of the invention, play between the shaft and the impeller is kept particularly low, along with an intended pivotability of the impeller, when the impeller is designed to be elastic at least in its radially inner region. In the most favorable case, the impeller may be pressed on the shaft. The elastic design of the radially inner region allows simple pivotability and axial movability of the radially outer edge of the impeller.
The elastic region of the impeller could be generated, for example, by the impeller having in this region an insert consisting of an elastic material. However, according to another advantageous development of the invention, the elastic region of the impeller is particularly cost-effective when the impeller has a groove arranged concentrically to the shaft.
Feed pumps often have substantially higher efficiency in one direction of rotation of the impeller than in the opposite direction of rotation. To ensure an intended high efficiency of the feed pump in a particularly simple way, the shaft and/or the impeller may have means for arranging them in the correct position. By virtue of this configuration, the impeller must be arranged in place on the shaft. Accordingly, the direction of rotation of the impeller is reliably fixed.
According to another embodiment of the present invention, the means for arranging the impeller in the correct position are configured in a particularly simple way in terms of design when the impeller has a projection, arranged near one of its end faces for engaging into a step-like recess of the shaft. The recess is configured according to the projection. Furthermore, the shaft is held axially nondisplaceably with respect to the casing. The casing may thereby be mounted only when the impeller is fastened in the correct position on the shaft.
According to yet another embodiment of the invention, the means for arranging the impeller in the correct position include two flattenings which are nonparallel and/or have different dimensions for connection to a correspondingly configured recess of the impeller. This configuration requires a particularly low outlay in terms of construction and the connection is positive in the direction of rotation.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.